Four men found at a large cannabis factory in Essex have been jailed.
Police raided a disused printing works at Heybridge near Maldon in November last year and found 8,000 plants with a potential street value of £2m.
Four men, all Vietnamese nationals, later admitted growing the plants between July and November 2010.
They were sentenced at Chelmsford Crown Court on Monday to jail terms ranging from three years and eight months to four years and eight months.
Police who raided the former printing works found the men looking after a crop of cannabis growing in a series of rooms.
Ho Vu Phong, 23, was jailed for four years and eight months, Tran Hung Van, 44, and Le Tuan Van, 40, for four years and Doan Nguyen Hai, 18, for three years and eight months.
All four had been of no fixed address at the time of their arrests.
DCI Simon Parkes, of Kent and Essex serious crime directorate, said: "These men were involved in the day-to-day running of one of the biggest, and certainly the most sophisticated, cannabis factories ever found in Essex.
"They were working full time and in complete secrecy in a former printing works to cultivate cannabis plants in various stages of growth.
"They had a potential street value of about £2m when fully grown.
"We estimate the people who set up this site had invested more than £250,000 on this factory.
"But their plans to cash in on the drugs black market were thwarted following some excellent surveillance and detective work by a team of locally-based officers."